When a neurological disease begins to affect a human body, few signs are noticeable that indicate that a particular human being has a neurological disease. Specifically, it may be years or even decades before the onset of otherwise observable symptoms. For example, the scientific community now thinks that the typical time between onset of the disease and diagnosable symptoms for Alzheimer's is 30 years. Research indicates that certain movement disorders are among the first symptoms of such neurological diseases. However, signs of movement disorders are difficult to observe and gather information on and uncertain in their predictive validity, until much later in the process of the disease.
Today, one particular method frequently used is the Finger Tapping Test (FTT). In its most common implementation, it is in essence a speed test. Patients are asked to tap with each index each of two levers, typically 20 centimeters apart, most often 5 times for each finger, at 10 seconds each time. Studies have shown that patients with brain disease perform more inconsistently on this test than control groups. More advanced versions of the FTT have included an analysis of consistency. Although the data is very limited, the findings indicate that consistency also declines with the onset of the disease.
The FTT test does deliver useful data, but it is very limited in its scope. Specifically, only two variables are measured (the number of taps during a 10/second period for each index finger). Typically, only 5 data points are captured for each variable (i.e. 5 10-second sessions) and each data point will be an integer between 20 and 70. One study has indicated that consistency is important, rather than speed and the FFT test delivers very limited consistency data. In the words of a major brain disease scientist: As we age, we get slower. But if we get more inconsistent, that is due to disease. The volume and granularity of FTT data is too low for early diagnosis. Also, since FTT requires in-person visits and special equipment, it is cumbersome and costly to use. Thus, FTT is not useful for detecting brain diseases early and accurately nor brain injuries on a continuous basis.